Insulation film on semiconductor substrate and method for forming same

ABSTRACT

An insulation film is formed on a semiconductor substrate by vaporizing a silicon-containing hydrocarbon compound to provide a source gas, introducing a reaction gas composed of the source gas and an additive gas such as an inert gas and oxidizing gas to a reaction space of a plasma CVD apparatus. The silicon-containing hydrocarbon compound includes a cyclosiloxan compound or a linear siloxan compound, as a basal structure, with reactive groups for form oligomers using the basal structure. The residence time of the reaction gas in the reaction space is lengthened by reducing the total flow of the reaction gas in such a way as to form a siloxan polymer film with a low dielectric constant.

This is a continuation-in-part of U.S. patent application Ser. No.10/288,641 filed Nov. 5, 2002, which is a continuation-in-part of U.S.patent application Ser. No. 09/827,616 filed Apr. 6, 2001 now U.S. Pat.No. 6,514,880, which is a continuation-in-part of (i) U.S. patentapplication Ser. No. 09/243,156 filed Feb. 2, 1999, now abandoned, whichclaims priority to Japanese patent application No. 37929/1998 filed Feb.5, 1998, (ii) U.S. application Ser. No. 09/326,847 filed Jun. 7, 1999,now U.S. Pat. No. 6,352,945, (iii) U.S. patent application Ser. No.09/326,848 filed Jun. 7, 1999, now U.S. Pat. No. 6,383,955, and (iv)U.S. patent application Ser. No. 09/691,376 filed Oct. 18, 2000, nowU.S. Pat. No. 6,432,846, all of which are incorporated herein byreference in their entirety. This application claims priority to all ofthe foregoing under 35 U.S.C. §119 and §120.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a semiconductor technique and moreparticularly to a silicone polymer insulation film on a semiconductorsubstrate and a method for forming the film by using a plasma CVD(chemical vapor deposition) apparatus.

2. Description of the Related Art

Because of the recent rise in requirements for the large-scaleintegration of semiconductor devices, a multi-layered wiring techniqueattracts a great deal of attention. In these multi-layered structures,however, capacitance among individual wires hinders high speedoperations. In order to reduce the capacitance it is necessary to reducerelative dielectric constant of the insulation film. Thus, variousmaterials having a relatively low relative dielectric constant have beendeveloped for insulation films.

Conventional silicon oxide films SiO_(x) are produced by a method inwhich oxygen O₂ or nitrogen oxide N₂O is added as an oxidizing agent toa silicon material gas such as SiH₄ or Si(OC₂H₅)₄ and then processed byheat or plasma energy. Its relative dielectric constant is about 4.0.

Alternatively, a fluorinated amorphous carbon film has been producedfrom C_(x)F_(y)H_(z) as a material gas by a plasma CVD method. Itsrelative dielectric constant ε is as low as 2.0-2.4.

Another method to reduce the relative dielectric constant of insulationfilm has been made by using the good stability of Si—O bond. Asilicon-containing organic film is produced from a material gas underlow pressure (1 Torr) by the plasma CVD method. The material gas is madefrom P-TMOS (phenyl trimethoxysilane, formula 1), which is a compound ofbenzene and silicon, vaporized by a babbling method. The relativedielectric constant ε of this film is as low as 3.1.

A further method uses a porous structure made in the film. An insulationfilm is produced from an inorganic SOG material by a spin-coat method.The relative dielectric constant ε of the film is as low as 2.3.

However, the above noted approaches have various disadvantages asdescribed below.

First, the fluorinated amorphous carbon film has lower thermal stability(370° C.), poor adhesion with silicon-containing materials and alsolower mechanical strength. The lower thermal stability leads to damageunder high temperatures such as over 400° C. Poor adhesion may cause thefilm to peel off easily. Further, the lower mechanical strength canjeopardize wiring materials.

Oligomers that are polymerized using P-TMOS molecules do not form alinear structure in the vapor phase, such as a siloxane structure,because the P-TMOS molecule has three O—CH₃ bonds. The oligomers havingno linear structure cannot form a porous structure on a Si substrate,i.e., the As a result, the relative dielectric constant of the filmcannot be reduced to a desired degree.

In this regard, the babbling method means a method wherein vapor of aliquid material, which is obtained by having a carrier gas such as argongas pass through the material, is introduced into a reaction chamberwith the carrier gas. This method generally requires a large amount of acarrier gas in order to cause the material gas to flow. As a result, thematerial gas cannot stay in the reaction chamber for a sufficient lengthof time to cause polymerization in a vapor phase.

Further, the SOG insulation film of the spin-coat method has a problemin that the material cannot be applied onto the silicon substrate evenlyand another problem in which a cure system after the coating process iscostly.

It is, therefore, a principal object of this invention to provide animproved insulation film and a method for forming it.

It is another object of this invention to provide an insulation filmthat has a low relative dielectric constant, high thermal stability,high humidity-resistance and high adhesive strength, and a method forforming it.

It is a further object of this invention to provide a material forforming an insulation film that has a low relative dielectric constant,high thermal stability, high humidity-resistance and high adhesivestrength.

It is a still further object of this invention to provide a method foreasily forming an insulation film that has a low relative dielectricconstant without requiring an expensive device.

SUMMARY OF THE INVENTION

One aspect of this invention involves a method for forming an insulationfilm on a semiconductor substrate by using a plasma CVD apparatusincluding a reaction chamber, which method comprises a step of directlyvaporizing a silicon-containing hydrocarbon compound expressed by thegeneral formula Si_(α)O_(β)C_(x)H_(y) (α, β, x, and y are integers) andthen introducing it to the reaction chamber of the plasma CVD apparatus,a step of introducing an additive gas, the flow volume of which issubstantially reduced, into the reaction chamber and also a step offorming an insulation film on a semiconductor substrate by plasmapolymerization reaction wherein mixed gases made from the vaporizedsilicon-containing hydrocarbon compound as a material gas and theadditive gas are used as a reaction gas. It is a remarkable feature thatthe reduction of the additive gas flow also results in a substantialreduction of the total flow of the reaction gas. According to thepresent invention, a silicone polymer film having a micropore porousstructure with low relative dielectric constant can be produced.

The present invention is also drawn to an insulation film formed on asemiconductor substrate, and a material for forming the insulation film,residing in the features described above.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught herein without necessarilyachieving other objects or advantages as may be taught or suggestedherein.

Further aspects, features and advantages of this invention will becomeapparent from the detailed description of the preferred embodimentswhich follow.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will now be described withreference to the drawings of preferred embodiments which are intended toillustrate and not to limit the invention.

FIG. 1 is a schematic diagram illustrating a plasma CVD apparatus usedfor forming an insulation film of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In an embodiment of the present invention, a method is provided to forman insulation film on a semiconductor substrate by plasma reaction andcomprises the steps of: (i) vaporizing a silicon-containing hydrocarboncompound to provide a source gas; (ii) introducing the source gas into areaction space for plasma CVD processing wherein a semiconductorsubstrate is placed; (iii) optionally introducing an additive gasselected from the group consisting of an inert gas and an oxidizing gas,said oxidizing gas being used in an amount less than the source gas,said source gas and said additive gas constituting a reaction gas; and(iv) forming an insulation film on the semiconductor substrate byactivating plasma polymerization reaction in the reaction space, whereinthe plasma polymerization reaction is activated while controlling theflow of the reaction gas to lengthen a residence time, Rt, of thereaction gas in the reaction space, wherein 100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/Fwherein Pr: reaction space pressure (Pa); Ps: standard atmosphericpressure (Pa); Tr: average temperature of the reaction gas (K); Ts:standard temperature (K); r_(w): radius of the silicon substrate (m); d:space between the silicon substrate and the upper electrode (m); F:total flow volume of the reaction gas (sccm).

In the present invention, the silicon-containing hydrocarbon compoundexpressed as the general formula Si_(α)O_(βC) _(x)H_(y) (α, β, x, and yare integers) can be any suitable compounds having structuresaccomplishing polymerization or oligomerization of the basal structuresof the compounds under prolonged residence time conditions. The basalstructure includes, but is not limited to, (i) a cyclosiloxan compoundwhich may preferably have the formula Si_(n)O_(n)R_(2n−m) wherein n isan integer of 3-6, m represents the number of a unsaturated bond betweenSi and C and is an integer of 0-6 (m≦n), and R is C₁₋₆ saturated orunsaturated hydrocarbon attached to Si, and (ii) a linear siloxancompound which may preferably have the formula Si_(α)O_(α−1)R_(2α−β+2)wherein α is an integer of 1-3, β is 0, 1, or 2 (β≦α), n is an integerof 1-3, and R is C₁₋₆ hydrocarbon attached to Si.

Reactive groups which form oligomers using the basal structures include,but are not limited to, alkoxy group such as —O—CH₃, unsaturatedhydrocarbon such as —CH═CH₂, amino group such as —NH₂, and acid radicalsuch as carboxylic radical —COOH and acetoxyl group —OOCCH₃. Thereactive group(s) and the basal structure can be included in a singlecompound or different compounds. That is, as long as the reactivegroup(s) and the basal structure exist and forms oligomers, compoundscan be used singly or in any combination.

For example, the silicon-containing hydrocarbon can be a mixture of acyclosiloxan compound (precursor 1) and an unsaturatedhydrocarbon-containing compound (precursor 2). By oligomerization ofprecursor 1 using precursor 2, wherein precursor 1 is linked to eachother using vinyl groups of precursor 2, a film comprised of oligomerscan be formed as described earlier. This film has a low dielectricconstant.

In the above, any suitable cyclosiloxan compound can be used, but thecyclosiloxan compound may preferably have the formulaSi_(n)O_(n)R_(2n−m) wherein n is an integer of 3-6, m represents thenumber of a unsaturated bond between Si and C and is an integer of 0-6(m≦n), and R is C₁₋₆ saturated or unsaturated hydrocarbon attached toSi. The compound has the structure —(SiR_(2-m/n)O_()n)— and may includehexamethylcyclotrisiloxane

In the above, the unsaturated hydrocarbon-containing compound has atleast one vinyl group. Such a unsaturated hydrocarbon may be selectedfrom the group consisting of compounds of the formula R¹ _(y)Si_(x)R²_(2x−y+2) and compounds of the formula C_(n)H_(2(n−m)+2), wherein R¹ isC₁₋₆ unsaturated hydrocarbon attached to Si, R² is C₁₋₆ saturatedhydrocarbon attached to Si, x is an integer of 1-4, y is an integer of1-2, n is an integer of 1-6, and m represents the number of unsaturatedcarbon bonds and is an integer of 1-5 (n≧m). The above unsaturatedhydrocarbon includes, but are not limited to, unsaturatedhydrocarbon-containing organosilicon such as (CH₃)₂Si(C₂H₃)₂,(C₂H₃)₂SiH₂, (C₆H₅)SiH₃, (C₆H₅)Si(CH₃)₃, (C₆H₅)₂Si(CH₃)₂, and(C₆H₅)₂Si(OCH₃)₂, and unsaturated hydrocarbon compounds such as C₂H₄,C₃H₄, C₃H₆, C₄H₈, C₃H₅(CH₃), and C₃H₄(CH)₂. The flow ratio of precursor1 (sccm) to precursor 2 (sccm) may be in the range of 0.1 to 10(including 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 5, and a range of any twoof the foregoing such as a range of 0.5 to 2).

In the above, oligomerization of the cyclosiloxan compound can beperformed with the reactive groups in a vaporous phase, therebydepositing an insulation film comprised of oligomers of the cyclosiloxancompound. According to the above embodiments, the insulation film canhave a dielectric constant of 2.7 or less, preferably 2.4 or less.

In another embodiment, the aforesaid basal structure and the reactivegroup(s) are included in a single compound. For example, in the generalformula (Si_(n)O_(n)R_(2n−m))X_(m), wherein X is —O—C_(p)H_(2p+1)wherein p is an integer of 1-4 (preferably 1 or 2) such as —O—CH₃, or—C₂H_(2(z-w)+2) wherein z is an integer of 1-4 (preferably 1 or 2), andw represents the number of unsaturated carbon bonds and is an integer of1-3 (preferably 1) such as —CH═CH₂. These compounds include1,3,5-trimethyl-1,3,5-trimethoxycyclotrisiloxane

and 1,3,5-trimethyl-1,3,5-trivinyilycyclotrisiloxane.

In the above, oligomerization of the cyclosiloxan compound can beperformed using their reactive groups in a vaporous phase, therebydepositing an insulation film comprised of oligomers of the cyclosiloxancompound. According to the above embodiments, the insulation film canhave a dielectric constant of 2.7 or less, preferably 2.4 or less.

In still another embodiment of the present invention, thesilicon-containing hydrocarbon compound may have, as the basalstructure, a linear siloxan compound which may preferably have theformula (Si_(α)O_(α−1)R_(2α−β+2))X_(β) or a cyclo-siloxan compound whichmay preferably have the formula (Si_(n)O_(n)R_(2n−m))X_(m), wherein X isa reactive group including, but not limited to, an amino group such as—NH₂, and an acid radical such as carboxylic radical —COOH and acetoxylgroup —OOCCH₃. These compounds includes H₂N—Si(CH₃)₂—NH₂ andCH₃COO—Si(CH₃)₂—OOCCH₃. In the above, if the amino group-containingcompound and the acid radical-containing compound are mixed,polymerization can be enhanced by acid-alkali reaction.

In the above, the reactive groups are attached to the basal structure ina single compound, but the reactive groups and the basal structure canbe different compounds wherein a reactive group gas is separately addedto a basal structure compound to cause oligomization by acid-alkalireaction. For example, the reactive group gas can be any suitable gasincluding N such as dimethylamine ((CH₃)₂NH), N,N-dimethylhydrazine((CH₃)₂NNH₂), ethylazide (C₂H₅N₃), methylamine (CH₃NH₂), andmethylhydrazine (CH₃NHNH₂).

A film formed from a precursor having an amino group and/or an acidradical can suitably be used in formation of a wiring structure. When adevice uses a low dielectric constant film, a resist is applied on a lowdielectric constant film which is then subjected to patterning andetching. Thereafter, the remaining resist is removed and washed out witha chemical solution. In addition to a resist, a sacrificial film may beapplied on the low dielectric film, which may also be removed with achemical solution simultaneously with the resist. The resist and thesacrificial film are organic, and thus their characteristics are similarto those of a low dielectric film (e.g., k<3) which often containsorganic materials. Thus, a chemical solution used for removing a resistand/or a sacrificial film may dissolve the low dielectric film.Accordingly, if a strong chemical solution is used in order to increasethe removal of the resist and/or sacrificial film, it is difficult toprotect the low dielectric film. Many chemical solutions are alkali oracidic. Thus, by rendering the low dielectric film the oppositecharacteristic, i.e., acidic against an alkali solution and alkaliagainst an acidic solution, decomposition of the low dielectric film caneffectively be prevented and protected. This is an example of effectiveuse of a film formed using a precursor having an amino group and/or acidradical as described above.

In the above, oligomerization of the cyclosiloxan compound can beperformed with the reactive groups in a vaporous phase, therebydepositing an insulation film comprised of oligomers of the cyclosiloxancompound. According to the above embodiments, the insulation film canhave a dielectric constant of 2.7 or less, preferably 2.4 or less.

Additionally, all of the aforesaid compounds and the reactive groups canbe used singly or in a combination of at least two of any compoundsand/or at least two of any reactive groups.

Compounds which can be mixed include a compound having at least one Si—Obond, two or less O—C_(n)H_(2n+1) bonds and at least two hydrocarbonradicals bonded with silicon (Si). A preferable silicon-containinghydrocarbon compound has formula:Si_(α)O_(α−1)R_(2α−β+2)(OC_(n)H_(2n+1))_(β)wherein α is an integer of 1-3, β is 0, 1, or 2, n is an integer of 1-3,and R is C₁₋₆ hydrocarbon attached to Si.

More specifically, the silicon-containing hydrocarbon compound includesat least one species of the compound expressed by the chemical formula(2) as follows:

wherein R1 and R2 are one of CH₃, C₂H₃, C₂H₅, C₃H₇ and C₆H₅, and n areany integer.

Except for the species indicated above, the silicon-containinghydrocarbon compound can include at least one species of the compoundexpressed by the chemical formula (3) as follows:

wherein R1, R2 and R3 are one of CH₃, C₂H₃, C₂H₅, C₃H₇ and C₆H₅, and nis any integer.

Except for those species indicated above, the silicon-containinghydrocarbon compound can include at least one species of the compoundexpressed by the chemical formula (4) as follows:

wherein R1, R2, R3 and R4 are one of CH₃, C₂H₃, C₂H₅, C₃H₇ and C₆H₅, andm and n are any integer.

Further, except for those species indicated above, thesilicon-containing hydrocarbon compound can include at least one speciesof the compound expressed by the chemical formula (5) as follows:

wherein R1, R2, R3, R4, R5 and R6 are one of CH₃, C₂H₃, C₂H₅, C₃H₇andC₆H₅, and the additive gases are argon (Ar), Helium (He) and eithernitrogen oxide (N₂O) or oxygen (O₂).

Furthermore, except for those species indicated above, thesilicon-containing hydrocarbon compound can include at least one speciesof the compound can include at least one species of the compoundexpressed by the chemical formula (6) as follows:

wherein R1, R2, R3 and R4 are one of CH₃, C₂H₃, C₂H₅, C₃H₇ and C₆H₅, andthe additive gases are argon (Ar), Helium (He) and either nitrogen oxide(N₂O) or oxygen (O₂).

Still further, the material gas can include at least one of saidsilicon-containing hydrocarbon compounds indicated above.

In accordance with another aspect of this invention, an insulation filmis formed on a substrate and the film is polymerized with plasma energyin a plasma CVD apparatus by using a material gas including asilicon-containing hydrocarbon compound expressed by formula 2.

Additionally, the insulation film is formed on a substrate and the filmis polymerized with plasma energy in a plasma CVD apparatus by using amaterial gas including a silicon-containing hydrocarbon compoundexpressed by formula 3.

Further, the insulation film is formed on a substrate and the film ispolymerized with plasma energy in a plasma CVD apparatus by using amaterial gas including a silicon-containing hydrocarbon compoundexpressed by formula 4.

Furthermore, the insulation film is formed on a substrate and the filmis polymerized with plasma energy in a plasma CVD apparatus by using amaterial gas including a silicon-containing hydrocarbon compoundexpressed by formula 5.

Still further, the insulation film is formed on a substrate and the filmis polymerized with plasma energy in a plasma CVD apparatus by using amaterial gas including a silicon-containing hydrocarbon compoundexpressed by formula 6.

In accordance with a further aspect of this invention, a material forforming an insulation film is supplied in a vapor phase in the vicinityof a substrate and is treated in a plasma CVD apparatus to form theinsulation film on the substrate by chemical reaction, and the materialis further expressed by formula 2.

Additionally, a material for forming an insulation film is supplied in avapor phase in the vicinity of a substrate and is treated in a plasmaCVD apparatus to form the insulation film on the substrate by chemicalreaction, and the material is further expressed by formula 3.

Further, a material for forming an insulation film is supplied in avapor phase in the vicinity of a substrate and is treated in a plasmaCVD apparatus to form the insulation film on the substrate by chemicalreaction, and the material is further expressed by formula 4.

Furthermore, a material for forming an insulation film is supplied in avapor phase with either nitrogen oxide (N₂O) or oxygen (O₂) as anoxidizing agent in the vicinity of a substrate and is treated i on saidsubstrate by chemical reaction, and this material can be the compoundexpressed by formula 5.

Still further, a material for forming an insulation film is supplied ina vapor phase with either nitrogen oxide (N₂O) or oxygen (O₂) as theoxidizing agent in the vicinity of a substrate and is treated on saidsubstrate by chemical reaction, and this material further can be thecompound expressed by formula 6.

The residence time of the reaction gas is determined based on thecapacity of the reaction chamber for reaction, the pressure adapted forreaction, and the total flow of the reaction gas. The reaction pressureis normally in the range of 1-10 Torr, preferably 3-7 Torr, so as tomaintain stable plasma. This reaction pressure is relatively high inorder to lengthen the residence time of the reaction gas. The total flowof the reaction gas is important to reducing the relative dielectricconstant of a resulting film. It is not necessary to control the ratioof the material gas to the additive gas. In general, the longer theresidence time, the lower the relative dielectric constant becomes. Thematerial gas flow necessary for forming a film depends on the desireddeposition rate and the area of a substrate on which a film is formed.For example, in order to form a film on a substrate [r(radius)=100 mm]at a deposition rate of 300 nm/min, at least 50 sccm of the material gasis expected to be included in the reaction gas. That is approximately1.6×10² sccm: per the surface area of the substrate (m²). The total flowcan be defined by residence time (Rt). When Rt is defined describedbelow, a preferred range of Rt is 100 msec≦Rt, more preferably 200msec≦Rt≦5 sec. In a conventional plasma TEOS, Rt is generally in therange of 10-30 msec.Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F

-   -   wherein:    -   Pr: reaction chamber pressure (Pa)    -   Ps: standard atmospheric pressure (Pa)    -   Tr: average temperature of the reaction gas (K)    -   Ts: standard temperature (K)    -   r_(w): radius of the silicon substrate (m)    -   d: space between the silicon substrate and the upper electrode        (m)    -   F: total flow volume of the reaction gas (sccm)

In the above, the residence time means the average period of time inwhich gas molecules stay in the reaction chamber. The residence time(Rt) can be calculated at Rt=αV/S, wherein V is the capacity of thechamber (cc), S is the volume of the reaction gas (cc/s), and α is acoefficient determined by the shape of the reaction chamber and thepositional relationship between the inlet of gas and the outlet ofexhaust. The space for reaction in the reaction chamber is defined bythe surface of the substrate (πr²) and the space between the upperelectrode and the lower electrode. Considering the gas flow through thespace for reaction, α can be estimated as ½. In the above formula, α is½.

In this method, the material gas is, in short, a silicon-containinghydrocarbon compound including at least one Si—O bond, at most twoO—C_(n)H_(2n+1) bonds and at least two hydrocarbon radicals bonded tothe silicon (Si). Also, this material gas is vaporized by a directvaporization method. The method results in an insulation film having alow relative dielectric constant, high thermal stability and highhumidity-resistance.

More specifically, the source gas vaporized by the direct vaporizationmethod can stay in the plasma for a sufficient length of time. As aresult, a linear polymer can be formed so that a linear polymer havingthe basic structure (formula 7), wherein the “n” is 2 or a greatervalue, forms in a vapor phase. The polymer is then deposited on thesemiconductor substrate and forms an insulation film having a microporeporous structure.

wherein X1 and X2 are O_(n)C_(m)H_(p) wherein n is 0 or 1, m and p areintegers including zero.

The insulation film of this invention has a relatively high stabilitybecause its fundamental structure has the Si—O bond having high bondingenergy therebetween. Also, its relative dielectric constant is lowbecause it has a micropore porous structure. Further, the fundamentalstructure (—SiO—)_(n) has, on both sides, dangling bonds ending with ahydrocarbon radical possessing hydrophobicity, and Furthermore, the bondof a hydrocarbon radical and silicon is generally stable. For instance,both the bond with a methyl radical, i.e., Si—CH₃, and bond withbenzene, i.e., Si—C₆H₅, have a dissociation temperature of 500° C. orhigher. Since above semiconductor production requires thermal stabilityto temperatures above 450° C., that property of the film is advantageousfor production of semiconductors.

Further aspects, features and advantages of this invention will becomeapparent from the detailed description of the preferred examples whichfollows.

FIG. 1 diagrammatically shows a plasma CVD apparatus usable in thisinvention. This apparatus comprises a reaction gas-supplying device 12and a plasma CVD device 1. The reaction gas-supplying device 12comprises plural lines 13, control valves 8 disposed in the lines 13,and gas inlet ports 14, 15 and 16. A flow controller 7 is connected tothe individual control valves 8 for controlling a flow of a material gasof a predetermined volume. A container accommodating liquid reactingmaterial 18 is connected to a vaporizer 17 that directly vaporizesliquid. The plasma CVD device 1 includes a reaction chamber 6, a gasinlet port 5, a susceptor 3 and a heater 2. A circular gas diffusingplate 10 is disposed immediately under the gas inlet port. The gasdiffusing plate 10 has a number of fine openings at its bottom face andcan inject reaction gas to the semiconductor substrate 4 therefrom.There is an exhaust port 11 at the bottom of the reaction chamber 6.This exhaust port 11 is connected to an outer vacuum pump (not shown) sothat the inside of the reaction chamber 6 can be evacuated. Thesusceptor 3 is placed in parallel with and facing the gas diffusingplate 10. The susceptor 3 holds a semiconductor substrate 4 thereon andheats it with the heater 2. The gas inlet port 5 is insulated from thereaction chamber 6 and connected to an outer high frequency power supply9. Alternatively, the susceptor 3 can be connected to the power supply9. Thus, the gas diffusing plate 10 and the susceptor 3 act as a highfrequency electrode and generate a plasma reacting field in proximity tothe surface of the semiconductor substrate 4.

A method for forming an insulation film on a semiconductor substrate byusing the plasma CVD apparatus of this invention comprises a step ofdirectly vaporizing silicon-containing hydrocarbon compounds expressedby the general formula Si_(α)O_(β)C_(x)H_(y) (α, β, x, and y areintegers) and then introducing it to the reaction chamber 6 of theplasma CVD device 1, a step of introducing an additive gas, whose flowis substantially reduced, into the reaction chamber 6 and also a step offorming an insulation film on a semiconductor substrate by plasmapolymerization reaction wherein mixed gases, made from thesilicon-containing hydrocarbon compound as a material gas and theadditive gas, are used as a reaction gas. It is a remarkable featurethat the reduction of the additive gas flow also renders a substantialreduction of the total flow of the reaction gas. This feature will bedescribed in more detail later.

The additive gases used in this embodiment, more specifically, are argongas and helium gas. Argon is principally used for stabilizing plasma,while helium is used for improving uniformity of the plasma and alsouniformity of thickness of the insulation film.

In the method described above, the first step of direct vaporization isa method wherein a liquid material, the flow of which is controlled, isinstantaneously vaporized at a vaporizer that is preheated. This directvaporization method requires no carrier gas such as argon to obtain adesignated amount of the material gas. This differs greatly with thebabbling method. Accordingly, a large amount of argon gas or helium gasis no longer necessary and this reduces the total gas flow of thereaction gas and then lengthens the time in which the material gas staysin the plasma. As a result, sufficient polymerizing reactions occur inthe vapor so that a linear polymer can be formed and a film having amicropore porous structure can be obtained.

In FIG. 1, inert gas supplied through the gas inlet port 14 pushes outthe liquid reacting material 18, which is the silicon-containinghydrocarbon compound, to the control valve 8 through the line 13. Thecontrol valve 8 controls the flow of the liquid reacting material 18with the flow controller 7 so that it does not exceed a predeterminedvolume. The reduced silicon-containing hydrocarbon compound 18 goes tothe vaporizer 17 to be vaporized by the direct vaporization methoddescribed above. Argon and helium are supplied through the inlet ports15 and 16, respectively, and the valve 8 controls the flow volume ofthese gases. The mixture of the material gas and the additive gases,which is a reaction gas, is then supplied to the inlet port 5 of theplasma CVD device 1. The space between the gas diffusing plate 10 andthe semiconductor substrate 4, both located inside of the reactionchamber 6 which is already evacuated, is charged with high frequency RFvoltages, which are preferably 13.4 MHz and 430 kHz, and the spaceserves as a plasma field. The susceptor 3 continuously heats thesemiconductor substrate 4 with the heater 2 and maintains the substrate4 at a predetermined temperature that is desirably 350-450° C. Thereaction gas supplied through the fine openings of the gas diffusingplate 10 remains in the plasma field in proximity to the surface of thesemiconductor substrate 4 for a predetermined time.

If the residence time is short, a linear polymer cannot be depositedsufficiently so that the film deposited on the substrate does not form amicropore porous structure. Since the residence time is inverselyproportional to the flow volume of the reaction gas, a reduction of theflow volume of the reaction gas can lengthen its residence time.

Extremely reducing the total volume of the reaction gas is effected byreducing the flow volume of the additive gas. As a result, the residencetime of the reaction gas can be lengthened so that a linear polymer isdeposited sufficiently and subsequently an insulation film having amicropore porous structure can be formed.

In order to adjust the reaction in the vapor phase, it is effective toadd a small amount of an inert gas, an oxidizing agent, or a reducingagent to the reaction chamber. Helium (He) and Argon (Ar) are inertgases and have different first ionization energies of 24.56 eV and 15.76eV, respectively. Thus, by adding either He or Ar singly or both incombination in predetermined amounts, the reaction of the material gasin the vapor phase can be controlled. Molecules of the reaction gasundergo polymerization in the vapor phase, thereby forming oligomers.The oligomers are expected to have a O:Si ratio of 1:1. However, whenthe oligomers form a film on the substrate, the oligomers undergofurther polymerization, resulting in a higher oxygen ratio. The ratiovaries depending on the relative dielectric constant or othercharacteristics of a film formed on the substrate.

The use of an oxidizing agent or a reducing agent is determineddepending on the target relative dielectric constant (3.30 or less,preferably 3.10 or less, more preferably 2.80 or less) of a siliconepolymer film and other characteristics such as stability of dielectricconstant and thermal stability. The O:Si ratio in the material gas isalso considered to select an oxidizing agent or a reducing agent, asdescribed above. Preferably, if the ratio is lower than 3:2, anoxidizing agent is used, whereas if the ratio is higher than 3:2, areducing agent is used. Further, an inert gas such as Ar and He is forcontrolling plasma reaction, but is not indispensable to form a siliconepolymer film. The flow of material gas and the flow of additive gas canalso vary depending on the plasma CVD apparatus. The appropriate flowcan be determined by correlating the relative dielectric constant of thesilicone polymer film with the residence time of the reaction gas(composed of the material gas and the additive gas). The longer theresidence time, the lower the dielectric constant becomes. A reductionrate of dielectric constant per lengthened residence time is changeable,and after a certain residence time, the reduction rate of dielectricconstant significantly increases, i.e., the dielectric constant sharplydrops after a certain residence time of the reaction gas. After thisdielectric constant dropping range, the reduction of dielectric constantslows down. This is very interesting. In the present invention, bylengthening residence time until reaching the dielectric constantdropping range based on a predetermined correlation between thedielectric constant of the film and the residence time of the reactiongas, it is possible to reduce the relative dielectric constant of thesilicone polymer film significantly.

EXAMPLE

An experiment was conducted as described below. In this experiment,octamethylcyclotetrasiloxane as a precursor 1 and (CH₃)₂Si(C₂H₃)₂ as aprecursor 2 were used as a source gas. An ordinary plasma CVD device(Aurora™, ASM Japan K.K.) was used as an experimental device. Theconditions for forming the film are as follows:

-   -   OMCTC (octamethylcyclotetrasiloxane): 160 sccm    -   DVDVS ((CH₃)₂Si(C₂H₃)₂): 80 sccm    -   He: 100 sccm    -   O₂: 0 sccm    -   RF power supply: 1500W (by overlaying 13.4 MHz power and 430 kHz        power)    -   Pr (reaction chamber pressure): 532 Pa    -   Tr (average temperature of the reaction gas): 673 K    -   r_(w) (radius of the silicon substrate): 0.1 m    -   d (space between the silicon substrate and the upper electrode):        0.024 m    -   F (total flow volume of the reaction gas): 340 sccm    -   Ps (standard atmospheric pressure): 1.01×10⁵ Pa    -   Ts (standard temperature): 273 K    -   Rt (residence time; Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r_(w) ²d/F): 160        ms

The dielectric constant of the resultant film was as low as 2.65, andthe RI (Refractive index) was 1.61.

Although this invention has been described in terms of certain examples,other examples apparent to those of ordinary skill in the art are withinthe scope of this invention. Accordingly, the scope of the invention isintended to be defined only by the claims that follow. The presentinvention includes various embodiments and are not limited to the aboveexamples. The present invention particularly includes, but are notlimited to, the following embodiments, and any combination of theforgoing embodiments and the following embodiments can readily beaccomplished:

1) A method is for forming an insulation film on a semiconductorsubstrate by plasma reaction and comprises the steps of: (i) vaporizinga silicon-containing hydrocarbon compound to provide a source gas; (ii)introducing the source gas into a reaction space for plasma CVDprocessing wherein a semiconductor substrate is placed; (iii) optionallyintroducing an additive gas selected from the group consisting of aninert gas and an oxidizing gas, said oxidizing gas being used in anamount less than the source gas, said source gas and said additive gasconstituting a reaction gas; and (iv) forming an insulation film on thesemiconductor substrate by activating plasma polymerization reaction inthe reaction space, wherein the plasma polymerization reaction isactivated while controlling the flow of the reaction gas to lengthen aresidence time, Rt, of the reaction gas in the reaction space, wherein100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/Fwherein Pr: reaction space pressure (Pa); Ps: standard atmosphericpressure (Pa); Tr: average temperature of the reaction gas (K); Ts:standard temperature (K); r_(w): radius of the silicon substrate (m); d:space between the silicon substrate and the upper electrode (m); F:total flow volume of the reaction gas (sccm).

In the above, the reaction space should not be limited to a physicallydefined single section, but should include any suitable space for plasmareaction. That is, as one of ordinary skill in the art readilyunderstands, the space is a functionally defined reaction space. Thespace may be comprised of a physically defined single section such asthe interior of a reactor, or physically defined multiple sectionscommunicated with each other for plasma reaction, such as the interiorof a remote plasma chamber and the interior of a reactor. Further, thespace includes the interior of piping connecting multiple sectionsthrough which a reaction gas passes. The interior of the reactorincludes only the space used for plasma reaction. Thus, if only a partof the reactor interior is used for plasma reaction where the reactor iscomposed of multiple sections, only the part used for plasma reactionconstitutes a reaction space. Further, the plasma reaction includes apreliminary reaction for plasma polymerization. For example, upstream ofa reactor, heating a reaction gas (e.g., 150° C. to 500° C., preferably200° C. to 300° C., in a pre-heater chamber), exciting a reaction gas(e.g., in a remote plasma chamber), or mixing an excited additive gasand a source gas (e.g., in a pre-heater chamber) is included in apreliminary reaction.

2) In the method according to Item 1, the source gas and the additivegas are separately introduced into the reaction space. The additive gasand the source gas can be mixed upstream of a reactor and introducedinto the reactor. However, they can be introduced separately, dependingon the configuration of a reactor. As long as the gases are not in areactive state, regardless of whether the additive gas and the sourcegas are mixed or separated, the space where the gases are present doesnot constitute a reaction space. At a point where additive gas and thesource gas are in contact in a reactive state, the reaction spacebegins. The reactive state includes states where the reaction gas isheated or excited, or the excited additive gas and the source gas aremixed, for example.

3) In the method according to Item 1 or 2, the plasma polymerizationreaction comprises exciting the reaction gas and depositing the film onthe substrate. As described above, the plasma polymerization reactionincludes a preliminary reaction such as excitation of the reaction gas.

4) In the method according to any one of Items 1-3, the reaction spacecomprises a space for exciting the reaction gas and a space fordepositing the film. In this embodiment, the reaction gas can be excitedin a remote plasma chamber installed upstream of a reactor, and the filmis deposited on the substrate in the reactor. The source gas and theadditive gas can be introduced into the remote plasma chamber. In thiscase, the reaction space is composed of the interior of the remoteplasma chamber, the interior of the reactor, and the interior of thepiping connecting the remote plasma chamber and the reactor. Because ofusing the interior of the remote plasma chamber, the interior of thereactor can be significantly reduced, and thus, the distance between theupper electrode and the lower electrode can be reduced. This leads tonot only downsizing the reactor, but also uniformly controlling a plasmaover the substrate surface. Any suitable remote plasma chamber and anysuitable operation conditions can be used in the present invention. Forexample, usable are the apparatus and the conditions disclosed in U.S.patent application Ser. Nos. 09/511,934 filed Feb. 24, 2000 and No.09/764,523 filed Jan. 18, 2001, U.S. Pat. No. 5,788,778, and U.S. Pat.No. 5,788,799. The disclosure of each of the above is incorporatedherein by reference in its entirety.

5) In the method according to Item 3 or 4, the excitation of thereaction gas comprises exciting the additive gas and contacting theexcited additive gas and the source gas. The excitation of the reactiongas can be accomplished in the reactor or upstream of the reactor. Asdescribed above, both the source gas and the additive gas can be excitedin a remote plasma chamber. Alternatively, the excitation of thereaction gas can be accomplished by exciting the additive gas in aremote plasma chamber and mixing it with the source gas downstream ofthe remote plasma chamber.

6) In the method according to any one of Items 1-3, the reaction spacecomprises a space for heating the reaction gas and a space for excitingthe reaction gas and depositing the film. In this embodiment, thereaction gas can be heated in a pre-heat chamber installed upstream of areactor, the reaction gas is excited in the reactor, and film isdeposited on the substrate in the reactor. The source gas and theadditive gas can be introduced into the pre-heater chamber. In thiscase, the reaction space is composed of the interior of the pre-heaterchamber, the interior of the reactor, and the interior of the pipingconnecting the pre-heater chamber and the reactor. Because of using theinterior of the pre-heater chamber, the interior of the reactor can besignificantly reduced, and thus, the distance between the upperelectrode and the lower electrode can be reduced. This leads to not onlydownsizing the reactor, but also uniformly controlling a plasma over thesubstrate surface. Any suitable remote plasma chamber and any suitableoperation conditions can be used in the present invention. For example,usable are the apparatus and the conditions disclosed in the aforesaidreferences.

7) In the method according to Item 6, the excitation of the reaction gascomprises exciting the additive gas and contacting the excited additivegas and the source gas. In this embodiment, the additive gas can beexcited in a remote plasma chamber, and the source gas is heated in apre-heater chamber where the excited additive gas and the source gas arein contact, and then the reaction gas flows into the reactor fordeposition of a film. In this case, deposition of unwanted particles ona surface of the remote plasma chamber, which causes a failure ofignition or firing, can effectively be avoided, because only theadditive gas is present in the remote plasma chamber. The source gas ismixed with the excited additive gas downstream of the remote plasmachamber. The reaction space may be composed of the interior from a pointwhere the excited additive gas and the source gas meet to an entrance tothe reactor, and the interior of the reactor.

8) In the method according to any one of Items 1-7, the additive gas canbe selected from the group consisting of nitrogen, argon, helium, andoxygen, but should not be limited thereto.

9) In the method according to any one of Items 1-8, the plasmapolymerization reaction is conducted at a temperature of 350-450° C.However, the suitable temperature varies depending on the type of sourcegas, and one of ordinary skill in the art could readily select thetemperature. In the present invention, polymerization includes anypolymerization of two or more units or monomers, includingoligomerization.

10) In the method according to any one of Items 1-9, the formation ofthe insulation film is conducted while maintaining a gas diffusing plateat a temperature of 150° C. or higher (e.g., 150° C. to 500° C.,preferably 200° C. to 300° C.), through which the reaction gas flowsinto the reaction space, so that the reaction is promoted. In the above,the gas diffusing plate (or showerhead) may be equipped with atemperature control device to control the temperature. Conventionally,the temperature of the showerhead is not positively controlled and isnormally 140° C. or lower when the temperature of the reaction space is350-450° C., for example.

11) In the method according to any one of Items 1-10, the residence timeis determined by correlating the dielectric constant with the residencetime. This embodiment has been described earlier. The followingembodiments also have been described earlier:

12) In the method according to any one of Items 1-11, the flow of thereaction gas is controlled to render the relative dielectric constant ofthe insulation film lower than 3.10.

13) In the method according to any one of Items 1-12, Rt is no less than165 msec or 200 msec.

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. Therefore, it should be clearly understood thatthe forms of the present invention are illustrative only and are notintended to limit the scope of the present invention.

1. A method for forming an insulation film on a semiconductor substrateby plasma reaction, comprising the steps of: vaporizing asilicon-containing hydrocarbon compound to provide a source gas, saidsilicon-containing hydrocarbon compound comprising a cyclosiloxancompound, as a basal structure, with reactive groups for formingoligomers using the basal structure; introducing the source gas into areaction space for plasma CVD processing wherein a semiconductorsubstrate is placed; optionally introducing an additive gas selectedfrom the group consisting of an inert gas and an oxidizing gas, saidoxidizing gas being used in an amount less than the source gas, saidsource gas and said additive gas constituting a reaction gas; andforming an insulation film on the semiconductor substrate by activatingplasma polymerization reaction in the reaction space, wherein the plasmapolymerization reaction is activated while controlling the flow of thereaction gas to lengthen a residence time, Rt, of the reaction gas inthe reaction space, wherein 100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F wherein: Pr: reaction spacepressure (Pa) Ps: standard atmospheric pressure (Pa) Tr: averagetemperature of the reaction gas (K) Ts: standard temperature (K) r_(w):radius of the silicon substrate (m) d: space between the siliconsubstrate and the upper electrode (m) F: total flow volume of thereaction gas (sccm).
 2. The method according to claim 1, wherein theinsulation film has a dielectric constant of 2.7 or less.
 3. The methodaccording to claim 2, wherein the insulation film has a dielectricconstant of 2.4 or less.
 4. The method according to claim 1, wherein Rtis no less than 165 msec.
 5. A method for forming an insulation film ona semiconductor substrate by plasma reaction, comprising the steps of:vaporizing a silicon-containing hydrocarbon compound to provide a sourcegas, said silicon-containing hydrocarbon compound comprising acyclosiloxan compound or a linear siloxan compound, as a basalstructure, with reactive groups for forming oligomers using the basalstructure; introducing the source gas into a reaction space for plasmaCVD processing wherein a semiconductor substrate is placed; optionallyintroducing an additive gas selected from the group consisting of aninert gas and an oxidizing gas, said oxidizing gas being used in anamount less than the source gas, said source gas and said additive gasconstituting a reaction gas; and forming an insulation film on thesemiconductor substrate by activating plasma polymerization reaction inthe reaction space, wherein the plasma polymerization reaction isactivated while controlling the flow of the reaction gas to lengthen aresidence time, Rt, of the reaction gas in the reaction space, wherein100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F wherein: Pr: reaction spacepressure (Pa) Ps: standard atmospheric pressure (Pa) Tr: averagetemperature of the reaction gas (K) Ts: standard temperature (K) r_(w):radius of the silicon substrate (m) d: space between the siliconsubstrate and the upper electrode (m) F: total flow volume of thereaction gas (sccm), wherein said reactive group is selected from thegroup consisting of alkoxy group, vinyl group, amino group, and acidradical.
 6. The method according to claim 5, wherein saidsilicon-containing hydrocarbon is a cyclosiloxan compound havingreactive groups.
 7. The method according to claim 6, wherein saidreactive group is selected from the group consisting of alkoxy group andvinyl group.
 8. The method according to claim 7, wherein saidsilicon-containing hydrocarbon has the formula(Si_(n)O_(n)R_(2n−m))X_(m), wherein n is an integer of 3-6, m representsthe number of a unsaturated bond between Si and C and is an integer of0-6 (m≦n), R is C₁₋₆ saturated or unsaturated hydrocarbon attached toSi, X is —O—C_(p)H_(2p+1) wherein p is an integer of 1-4 or—C_(z)H_(2(z-w)+2) wherein z is an integer of 1-4, and w represents thenumber of unsaturated carbon bonds and is an integer of 1-3.
 9. Themethod according to claim 6, wherein said reactive group is selectedfrom the group consisting of amino group and acid radical.
 10. Themethod according to claim 9, wherein the reactive group is included in adifferent compound from the silicon-containing hydrocarbon.
 11. Themethod according to claim 9, wherein the reactive group is included inthe silicon-containing hydrocarbon.
 12. The method according to claim 5,wherein said silicon-containing hydrocarbon is a linear siloxan compoundhaving reactive groups.
 13. The method according to claim 12, whereinsaid reactive group is selected from the group consisting of amino groupand acid radical.
 14. The method according to claim 12, wherein saidlinear siloxan compound has the formula Si_(α)O_(α−1)R_(2α−β+2) whereinα is an integer of 1-3, β is 0, 1, or 2 (β≦α), n is an integer of 1-3,and R is C₁₋₆ hydrocarbon attached to Si.
 15. A method for forming aninsulation film on a semiconductor substrate by plasma reaction,comprising the steps of: vaporizing a silicon-containing hydrocarboncompound to provide a source gas, said silicon-containing hydrocarboncompound comprising a cyclosiloxan compound or a linear siloxancompound, as a basal structure, with reactive groups for formingoligomers using the basal structure; introducing the source gas into areaction space for plasma CVD processing wherein a semiconductorsubstrate is placed; optionally introducing an additive gas selectedfrom the group consisting of an inert gas and an oxidizing gas, saidoxidizing gas being used in an amount less than the source gas, saidsource gas and said additive gas constituting a reaction gas; andforming an insulation film on the semiconductor substrate by activatingplasma polymerization reaction in the reaction space, wherein the plasmapolymerization reaction is activated while controlling the flow of thereaction gas to lengthen a residence time, Rt, of the reaction gas inthe reaction space, wherein 100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F wherein: Pr: reaction spacepressure (Pa) Ps: standard atmospheric pressure (Pa) Tr: averagetemperature of the reaction gas (K) Ts: standard temperature (K) r_(w):radius of the silicon substrate (m) d: space between the siliconsubstrate and the upper electrode (m) F: total flow volume of thereaction gas (sccm), wherein said silicon-containing hydrocarbon is amixture of a cyclosiloxan compound and an unsaturatedhydrocarbon-containing compound.
 16. The method according to claim 15,wherein the cyclosiloxan compound has the formula Si_(n)O_(n)R_(2n−m),wherein n is an integer of 3-6, m represents the number of a unsaturatedbond between Si and C and is an integer of 1-6 (m≦n), and R is C₁₋₆saturated or unsaturated hydrocarbon attached to Si.
 17. The methodaccording to claim 15, wherein the unsaturated hydrocarbon-containingcompound has at least one vinyl group.
 18. The method according to claim15, wherein the polymerization is oligomerization of the cyclosiloxancompound, thereby forming an insulation film comprised of oligomers ofthe cyclosiloxan compound.
 19. A method for forming an insulation filmon a semiconductor substrate by plasma reaction, comprising the stepsof: vaporizing a silicon-containing hydrocarbon compound to provide asource gas, said silicon-containing hydrocarbon compound comprising acyclosiloxan compound or a linear siloxan compound, as a basalstructure, with reactive groups for forming oligomers using the basalstructure; introducing the source gas into a reaction space for plasmaCVD processing wherein a semiconductor substrate is placed; optionallyintroducing an additive gas selected from the group consisting of aninert gas and an oxidizing gas, said oxidizing gas being used in anamount less than the source gas, said source gas and said additive gasconstituting a reaction gas; and forming an insulation film on thesemiconductor substrate by activating plasma polymerization reaction inthe reaction space, wherein the plasma polymerization reaction isactivated while controlling the flow of the reaction gas to lengthen aresidence time, Rt, of the reaction gas in the reaction space, wherein100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F wherein: Pr: reaction spacepressure (Pa) Ps: standard atmospheric pressure (Pa) Tr: averagetemperature of the reaction gas (K) Ts: standard temperature (K) r_(w):radius of the silicon substrate (m) d: space between the siliconsubstrate and the upper electrode (m) F: total flow volume of thereaction gas (sccm), wherein the additive gas is used and introducedinto the reaction space separately from the reaction gas.
 20. The methodaccording to claim 19, wherein the excitation of the reaction gascomprises exciting the additive gas and contacting the excited additivegas and the source gas.
 21. The method according to claim 19, whereinthe additive gas is selected from the group consisting of nitrogen,argon, helium, and oxygen.
 22. A method for forming an insulation filmon a semiconductor substrate by plasma reaction, comprising the stepsof: vaporizing a silicon-containing hydrocarbon compound to provide asource gas, said silicon-containing hydrocarbon compound comprising acyclosiloxan compound or a linear siloxan compound, as a basalstructure, with reactive groups for forming oligomers using the basalstructure; introducing the source gas into a reaction space for plasmaCVD processing wherein a semiconductor substrate is placed; optionallyintroducing an additive gas selected from the group consisting of aninert gas and an oxidizing gas, said oxidizing gas being used in anamount less than the source gas, said source gas and said additive gasconstituting a reaction gas; and forming an insulation film on thesemiconductor substrate by activating plasma polymerization reaction inthe reaction space, wherein the plasma polymerization reaction isactivated while controlling the flow of the reaction gas to lengthen aresidence time, Rt, of the reaction gas in the reaction space, wherein100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F wherein: Pr: reaction spacepressure (Pa) Ps: standard atmospheric pressure (Pa) Tr: averagetemperature of the reaction gas (K) Ts: standard temperature (K) r_(w):radius of the silicon substrate (m) d: space between the siliconsubstrate and the upper electrode (m) F: total flow volume of thereaction gas (sccm), wherein the plasma polymerization reactioncomprises exciting the reaction gas and depositing the film on thesubstrate.
 23. A method for forming an insulation film on asemiconductor substrate by plasma reaction, comprising the steps of:vaporizing a silicon-containing hydrocarbon compound to provide a sourcegas, said silicon-containing hydrocarbon compound comprising acyclosiloxan compound or a linear siloxan compound, as a basalstructure, with reactive groups for forming oligomers using the basalstructure; introducing the source gas into a reaction space for plasmaCVD processing wherein a semiconductor substrate is placed; optionallyintroducing an additive gas selected from the group consisting of aninert gas and an oxidizing gas, said oxidizing gas being used in anamount less than the source gas, said source gas and said additive gasconstituting a reaction gas; and forming an insulation film on thesemiconductor substrate by activating plasma polymerization reaction inthe reaction space, wherein the plasma polymerization reaction isactivated while controlling the flow of the reaction gas to lengthen aresidence time, Rt, of the reaction gas in the reaction space, wherein100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F wherein: Pr: reaction spacepressure (Pa) Ps: standard atmospheric pressure (Pa) Tr: averagetemperature of the reaction gas (K) Ts: standard temperature (K) r_(w):radius of the silicon substrate (m) d: space between the siliconsubstrate and the upper electrode (m) F: total flow volume of thereaction gas (sccm), wherein the reaction space comprises a space forexciting the reaction gas and a space for depositing the film.
 24. Amethod for forming an insulation film on a semiconductor substrate byplasma reaction, comprising the steps of: vaporizing asilicon-containing hydrocarbon compound to provide a source gas, saidsilicon-containing hydrocarbon compound comprising a cyclosiloxancompound or a linear siloxan compound, as a basal structure, withreactive groups for forming oligomers using the basal structure;introducing the source gas into a reaction space for plasma CVDprocessing wherein a semiconductor substrate is placed; optionallyintroducing an additive gas selected from the group consisting of aninert gas and an oxidizing gas, said oxidizing gas being used in anamount less than the source gas, said source gas and said additive gasconstituting a reaction gas; and forming an insulation film on thesemiconductor substrate by activating plasma polymerization reaction inthe reaction space, wherein the plasma polymerization reaction isactivated while controlling the flow of the reaction gas to lengthen aresidence time, Rt, of the reaction gas in the reaction space, wherein100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F wherein: Pr: reaction spacepressure (Pa) Ps: standard atmospheric pressure (Pa) Tr: averagetemperature of the reaction gas (K) Ts: standard temperature (K) r_(w):radius of the silicon substrate (m) d: space between the siliconsubstrate and the upper electrode (m) F: total flow volume of thereaction gas (sccm), wherein the reaction space comprises a space forheating the reaction gas and a space for exciting the reaction gas anddepositing the film.
 25. A method for forming an insulation film on asemiconductor substrate by plasma reaction, comprising the steps of:vaporizing a silicon-containing hydrocarbon compound to provide a sourcegas, said silicon-containing hydrocarbon compound comprising acyclosiloxan compound or a linear siloxan compound, as a basalstructure, with reactive groups for forming oligomers using the basalstructure; introducing the source gas into a reaction space for plasmaCVD processing wherein a semiconductor substrate is placed; optionallyintroducing an additive gas selected from the group consisting of aninert gas and an oxidizing gas, said oxidizing gas being used in anamount less than the source gas, said source gas and said additive gasconstituting a reaction gas; and forming an insulation film on thesemiconductor substrate by activating plasma polymerization reaction inthe reaction space, wherein the plasma polymerization reaction isactivated while controlling the flow of the reaction gas to lengthen aresidence time, Rt, of the reaction gas in the reaction space, wherein100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F wherein: Pr: reaction spacepressure (Pa) Ps: standard atmospheric pressure (Pa) Tr: averagetemperature of the reaction gas (K) Ts: standard temperature (K) r_(w):radius of the silicon substrate (m) d: space between the siliconsubstrate and the upper electrode (m) F: total flow volume of thereaction gas (sccm), wherein the plasma polymerization reaction isconducted at a temperature of 350-450° C.
 26. A method for forming aninsulation film on a semiconductor substrate by plasma reaction,comprising the steps of: vaporizing a silicon-containing hydrocarboncompound to provide a source gas, said silicon-containing hydrocarboncompound comprising a cyclosiloxan compound or a linear siloxancompound, as a basal structure, with reactive groups for formingoligomers using the basal structure; introducing the source gas into areaction space for plasma CVD processing wherein a semiconductorsubstrate is placed; optionally introducing an additive gas selectedfrom the group consisting of an inert gas and an oxidizing gas, saidoxidizing gas being used in an amount less than the source gas, saidsource gas and said additive gas constituting a reaction gas; andforming an insulation film on the semiconductor substrate by activatingplasma polymerization reaction in the reaction space, wherein the plasmapolymerization reaction is activated while controlling the flow of thereaction gas to lengthen a residence time, Rt, of the reaction gas inthe reaction space, wherein 100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F wherein: Pr: reaction spacepressure (Pa) Ps: standard atmospheric pressure (Pa) Tr: averagetemperature of the reaction gas (K) Ts: standard temperature (K) r_(w):radius of the silicon substrate (m) d: space between the siliconsubstrate and the upper electrode (m) F: total flow volume of thereaction gas (sccm), wherein the formation of the insulation film isconducted while maintaining a gas diffusing plate at a temperature of150° C. or higher, through which the reaction gas flows into thereaction space.
 27. A method for forming an insulation film on asemiconductor substrate by plasma reaction, comprising the steps of:vaporizing a silicon-containing hydrocarbon compound to provide a sourcegas, said silicon-containing hydrocarbon compound comprising acyclosiloxan compound or a linear siloxan compound, as a basalstructure, with reactive groups for forming oligomers using the basalstructure; introducing the source gas into a reaction space for plasmaCVD processing wherein a semiconductor substrate is placed; optionallyintroducing an additive gas selected from the group consisting of aninert gas and an oxidizing gas, said oxidizing gas being used in anamount less than the source gas, said source gas and said additive gasconstituting a reaction gas; and forming an insulation film on thesemiconductor substrate by activating plasma polymerization reaction inthe reaction space, wherein the plasma polymerization reaction isactivated while controlling the flow of the reaction gas to lengthen aresidence time, Rt, of the reaction gas in the reaction space, wherein100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F wherein: Pr: reaction spacepressure (Pa) Ps: standard atmospheric pressure (P) Tr: averagetemperature of the reaction gas (K) Ts: standard temperature (K) r_(w):radius of the silicon substrate (m) d: space between the siliconsubstrate and the upper electrode (m) F: total flow volume of thereaction gas (sccm), wherein the residence time is determined bycorrelating the dielectric constant with the residence time.
 28. Amethod for forming an insulation film on a semiconductor substrate byplasma reaction, comprising the steps of: vaporizing asilicon-containing hydrocarbon compound to provide a source gas, saidsilicon-containing hydrocarbon compound comprising a cyclosiloxancompound or a linear siloxan compound, as a basal structure, withreactive groups for forming oligomers using the basal structure;introducing the source gas into a reaction space for plasma CVDprocessing wherein a semiconductor substrate is placed; optionallyintroducing an additive gas selected from the group consisting of aninert gas and an oxidizing gas, said oxidizing gas being used in anamount less than the source gas, said source gas and said additive gasconstituting a reaction gas; and forming an insulation film on thesemiconductor substrate by activating plasma polymerization reaction inthe reaction space, wherein the plasma polymerization reaction isactivated while controlling the flow of the reaction gas to lengthen aresidence time, Rt, of the reaction gas in the reaction space, wherein100 msec≦Rt,Rt[s]=9.42×10⁷(Pr·Ts/Ps·Tr)r _(w) ² d/F wherein: Pr: reaction spacepressure (Pa) Ps: standard atmospheric pressure (Pa) Tr: averagetemperature of the reaction gas (K) Ts: standard temperature (K) r_(w):radius of the silicon substrate (m) d: space between the siliconsubstrate and the upper electrode (m) F: total flow volume of thereaction gas (sccm), wherein the source gas comprises at least twocompounds selected from the group consisting of cyclosiloxan compoundsand linear siloxan compounds.